As those headlines suggest, the Pew results were put through the political spin cycle the moment they came out. Liberals tended to focus on the upbeat finding that most of the nation's 2.3 million Muslims are blending successfully into the American mainstream. Conservatives were more likely to home in on the troubling evidence that a minority of American Muslims, especially among those under 30, defend terrorism and support radical Islam.

The news that Muslims in the United States, two-thirds of whom were born abroad, are assimilating in the American melting pot and happy with their lives here should be welcomed by Americans left and right.

According to the Pew survey, 72 percent of US Muslims rate their community an "excellent" or "good" place to live, and 71 percent believe in the American work ethic -- you can get ahead in America if you're willing to work hard. More than six in 10 see no conflict between a devout Muslim and living in a modern society, and 62 percent say it is acceptable for Muslims to marry outside their faith. (Under Islamic law, Muslim women may not marry non-Muslims.)

There's more. "With the exception of very recent immigrants," Pew notes, most Muslims "report that a large proportion of their closest friends are non-Muslims." A plurality (43 percent) believes that "Muslims coming to the US should try and adopt American customs, rather than trying to remain distinct from the larger society." An even larger plurality (49 percent) says that mosques should "keep out of political matters" and not "express their views on day-to-day social and political questions."

All of which is reassuring evidence that the assimilative traditions and institutions in American life are still doing their job. It is good to see that the American paradigm of E Pluribus Unumencompasses Muslims, too.

Unfortunately, the good news in this survey doesn't neutralize the bad. And the bad news is that a small but alarming minority of American Muslims express support for jihadist terror and its perpetrators.

Asked whether suicide bombing and other forms of terrorism that target civilians can be justified "to defend Islam from its enemies," 78 percent answered "never." But 1 percent said such massacres can "often" be justified, 7 percent said "sometimes," and 5 percent said "rarely." Another 9 percent declined to answer. Among younger Muslims, the numbers were even worse. Only 69 percent flatly condemned all Islamist terror. More than one in four -- 26 percent -- endorsed jihadist murder in at least some circumstances.

Equally distressing: 5 percent of US Muslims have a favorable opinion of Al-Qaeda, while 27 percent refuse to give an opinion. Support for Osama bin Laden's lethal network is actually higher among US-born Muslims than among immigrants -- and highest of all among black American Muslims.

Who was responsible for 9/11? Only 40 percent of American Muslims will acknowledge that Arab terrorists committed the worst terrorist attack in US history. An astonishing 60 percent either deny that Arabs were involved or decline to answer the question.

It has been endlessly reiterated that the vast majority of Muslims are peaceful, moderate, and no threat to anyone. That is assuredly true. It is also true that a minority of Muslims espouses radical and dangerous beliefs, and some of them are prepared to translate those beliefs into violence.

A few Muslim men, mostly Saudi, were all it took to murder 3,000 Americans and wreak billions of dollars in damage on 9/11. A handful of Muslims, inflamed by jihadist teachings, sufficed to carry out most Islamist atrocities of the past 30 years. A minority can commit great evil -- especially when it lives amidst a majority that doesn't challenge its hateful ideology and confront those who promote it.

In the Pew survey, only 8 percent of American Muslims said terrorism in the name of Islam is often or sometimes justifiable. But 8 percent of 2.3 million Muslims is 184,000 people who support suicide bombings and beheadings in at least some instances. That is not a trivial threat. And it cannot be effectively suppressed unless the moderate Muslim mainstream actively repudiates and anathematizes Islamist ideas.

Like all cancers, the malignancy of radical Islam starts small. Happily, the American Muslim body politic has the strength and resources to defeat it. The question is, does it have the will?